Production of natural color photographs by intermediate dye coupling



Patented July -1 5, 1941 PRODUCTION OF NATURAL COLOR PHOTO- GRAPHS BY INTERMEDIATE DYE' COU- PLING Karl Schinzel, Silesia, Czechoslovakia, assignor to Eastman Kodak Company, Rochester, N. Y.,-

a corporation of New Jersey No Drawing. Application December 2, 1937, Se-

rial No. 177,738.

In AustriaDecember 3, 1936 A disadvantage of the methods of color photography by fast coupling or eliminative coupling, as described in my patent applicationSeri-al No. 151,811 and in Lichtbild (published by Rimpler, Haida) 1936, p. 53, is that the auxiliary group attached to the specific dye is not always entirely stable to the oxidising agents necessary for regeneration of the dye from its leuco-form, and that the Purity of the color and the fastness of the original vat dye may be affected by union with a quinone group. This disadvantage is, however, not of great importance and maybe entirely avoided if the temporary connected couplin group is split ofi during the dyeing process, or in the simplest case, during restoration of the specific image dye. This can be effected by oxidation or hydrolysis or by the simultaneous action of both, and in rare cases also by reduction.

Undoubtedly, the most ideal method of color photography would be to render the leuco dye of the image easily soluble inthe sodium carbonate of the developing solution during the first development, so that it may be washed out during development and a natural color photograph produced immediately after rc-oxidation of the residual leuco-body. This, however, generally presupposes the presence of carboxylicor sulphonic acid.or halide groups in the developing solution in addition to the hydroxyl, as for example, p-amino salicylic acid tive. This is, however, accompanied by an undesirable affinity to gelatine due to the enlargemonia, if the residual (leuco),-dye derivative has been previously coupled with p-amino-dimethylaniline to the completely insoluble indamine, either assisted by the residual silver halide after exposure or appropriate preliminary treatment, or by oxidation in any other manner, also by the action of nitrosodimethylaniline or diazo compounds,- provided this results in o-azo dyes insoluble in alkali, as in fl-naphthol derivatives or those of 'a-naphthol having a stable substituent in the 4-position. 1,2-dioxy-naphthalene- 4-sulphonic acid may be used for eliminative coupling of amines; in certain cases this may also be done with acid methylene groups attached or with the yellow developer 4-amino-laryl-3-alkyl-5-pyrazolone oxidising its residue to the dye. Primary first development with a neutral or very weakly acid developing solution is, of course, possible as also in all subsequently described modifications. Subsequent coupling development results at once into correctly col- (compare B/40/4740, 42/2746, 3188) or its o-chloro-derivament ofthe molecule during indamine formation,

which prolongs the washing out process considerably. Substitution of the developer by several hydroxyl groups, as'in 4-amino resorcin, is usually insufiicient- 'for obtaining the necessary solubility in aqueous sodium carbonate solution. Developer's obtained by the action of chlorides of carboxylic acids of resorcin or phloroglucin on p-nitro-m-amino-phenol and subsequent reduction, or on the product of p-nitraniline andtwo molecules of ethylene oxide, or by the reaction of sulphochlorides on p-nitraniline with subsequent reduction, are not suitable. The removal of the residual leuco-derivative after primary coupling can be facilitated by coupling with developing substances or diazo compounds containing a large amount'of hydroxyl. Washing away of the first produced coupling product with sodium carbonate is, however, not absolutely necessary; it may also be done with lye or am- 'ored positive images.

After printing of the complementary colored negatives obtained in the primary color coupling on a triple layer, the correctly colored positive is formed in the same manner.

In the preceding paragraph, the re-formation of the true image dye from its couplingleuco-derivative by splitting of the auxiliary coupling group has been described, which is usually efiected by oxidation in order to combine the re-oxidation of the leuco-form with it and, where possible, also the elimination of the reduced silver. Another method of freeing the silver from the coupling product is possible with quinone dyes, namely, by splitting the insoluble indamine or indophenol formed during development with dilute acid. This dispenseswith the necessity of combination with a special coupling group, since phenols, naphthols or their higher molecular derivatives reacting in the development coupling may themselves-be substituted in such a way that the quinone split 01f later by acid. possesses dye characteristics. A common factor of both methods is the formation of the final image by doing away with the coupling product as described in sections V and VI of the specification.

Gelatine is not affected by washing with sodium carbonate or ammonia and only slightly by alcoholic and acetonlc lye solution, provided it does not contain too much water. The splitting of alkyls, acyls or phenols from leuco-derivatives, preferably with an oxidising agent,l

often requires the use of dilute ammonia, alcosuch cases.

holic or dilute-alcoholic lye or alcoholic hydrochloric acid which, however, presumes insolubility of the liberated leuco-form of the vat dye or of the vatdye itself in these solutions. Tanning of the triple layer with formaline, dialdehyde or other reagents is always recommended in Diffusion of these reagents is only slightly retarded, due to thinness of the triple layer which, despite its 5-6 single layers, can be kept to the thickness of the average negative emulsion. Moderate warming to about 5060 naturally favours the desired progress of the reaction considerably. Three superimposed collodion-emulsion layers differing in their solubility and consisting of nitroacetyl cellulose,

acetylor ether cellulose and capable of emulsi- -fying silver halide,.are still more suitable, even if the general and color sensitivity can only be moderately exploited by high sensitization with dyes, or by ultraand hypersensitization means. In addition to the cellulose derivatives mentioned, also agar, polyvinyl acetate or other synthetic colloids can replace the gelatine in one, two or all three layers. In order to keep the collodion layers and similar substances sufficiently penetrable to the developing solutions, they are coated with dextrine, gum arabic, starchsugar, gelatine, etc., which may be washed off, or they are previously softened by alcohol, provided the components'are insoluble in it.

If the coupling groups are diflicult to deoxidize, vat dyes are employed for the formation of the corresponding leuco-derivatives which are very stable to oxidizing agents, as for example, those of the indanthroneand benzanthrone group, algols, highly-halogenated thioindigo dyes, etc. The leuco-forms of vat dyes are generally prepared with the aid of hydrosulphiteand sodium carbonate or lye, and an addition of alcohol or acetone often favours reduction. Algols and other simple anthraquinone'dyes are also reduced to the anthra-hydroquinone form in this manner. Other methods are available for the reduction to the anthranol and anthrone form, and the following references indicate the corresponding methods which are concerned. (358/2669, 75, 54/2327, 45/2843, 38/1797, 16/366, 703, Ann. 420/1, 134, 418/30, 396/141, 379/55, 330/177, 307/313, 160/148, Monatshefte 1. Ch. 1916/555, German Patents 330,550, 216,772, 201,- 542,194,197, 190,656).

If the leuco-derivatives of the vat dyes are not entirely colorless, or at least yellow, but show a color different from the genuine dye and sometimes even complementary to it, as is often the case in anthraquinone dyes, they can still be used in photography in such emulsions as they are transparent to the rays of this color.

The coupling speed is increased by the addinamic acid chloride but even more so the o-vinylbenzyl-bromide which can now be prepared fairly easily. Both these halide derivatives can be combined, either before or after polymerization, with amino-phenols, amino-a-naphthols, salicylamide, sodium-u-naphtholsulphamide, etc., or with those leuco-dye derivatives which contain.

an amino group in addition to the coupling hydroxyl group primarily reacting with it, as for example, the condensation product of substituted anthrone and amino-salicyclic aldehyde or naphthol aldehydes with one amino group in the second nucleus, or with the carbamide acid esters of leuco-vat dyes. The easily prepared o-vinyl-benzylamine can also be allowed to react with mesa-acid chlorides of anthrone or its substitution product, or, of course, with sallcoyl chloride, e-naphthol-2-carboxylic acid chloride, etc. The combination with derivatives of vinyl ether contained in the groups of N-oxyethylaniline, 8-hydroxyquinoline, and the like, are capable of coupling, but are less practical for this purpose. Distearines and analogous products of mannite dichlorhydrine, also low nitroor alkyl ether cclluloses with free hydroxyl groups can be used for this purpose and for combination with coupling acid chlorides.

Compounds substantively forming in the gelatine and hardly diffusing, even in the presence of sodium carbonate, ammonia or alkali, can be obtained by introducing sulphonic or-carboxylic acid groups into these highly-colloidal or also simpler coupling leuco-derivatives. They are prepared with the aid of salicylic sulphochloride, a-naphthol-4-sulphonicor 2-carboxylic acid chloride.

Any harmful effect on the sensitivity can be avoided with certainty by the addition of these and other not completely insoluble coupling derivatives of dyes to the layers in the form of completely insoluble salts with quinine, cinchonine, dicinchonine, etc., which are decomposed by the sodium carbonate or lye of the developing solution, however, so that they are present to a certain extent in pseudo-solution during the coupling process.

It has already been mentioned in application Serial No. 151,811 that reduced indamines, etc., can also be added to the layers as leuco-developers, developing with sodium carbonate to the dye which later is destroyed by acid; the residue of the leuco-compound is then oxidized to the dye, preferably with potassium ferricyanide containing sodium carbonate, or, if necessary, with the addition of thiosulphate. This process has no application here. In this and other methods described in V and VI, processes could be combined for generating a chromophore by acid splitting, also combined with the previously described process, using acid-stable leuco-developers added to one or two layers, as for example,

high-molecular insoluble homologues of o-amino-symmetrical m-xylenol, reduced carbazolindophenols, p hydroxynaphthoquinoneimides, azomethides, etc. The residual leuco-compound or component is removed by alkali after generation of the quinone dyes in the other layers, unless it can be left in the image.

It is known that a higher-molecular insoluble analogue of p-amino-dimethylaniline can be added to the lower layer, a similar analogue of p-aminophenol to the middle layer and reduced azomethine of an acetic acid derivative to the upper layer, and the desired component images are obtained by bathing in a dilute-alcoholic solution of u-naphthol containing sodium carbonate. This method is not of any particular advantage in the present case.

The coupling derivatives with a splitting acid methylene group or a pyrazolone residue are described in the following paragraphs. They can be used for fast coupling and eliminative coupling wtih many leuco-dyes without removing the coupling group, as described in application Serial No. 151,811, because the ketones formed during acid splitting are usually only weakly colored.

The leuco-compounds with splitting coupling group, which are described later, can be added to the layers also in connection with the other known color-photographic processes. It, is then, of course, unnecessary to introduce a hydroxyl-, arylsulphonylamino group, etc., which is usuallyv necessary for coupling, into the molecule.

The triple, double and grain layers described in applications Serial No. 139,758, 139,759 and 151,- 811, are suitable for application to the present processes. r

Exactly as indicated there, the sensitizers or any filter dyes are precipitated in the layers as insoluble salts, especially that partwhich is not adsorbed by the silver bromide grain. Precipitants for the sensitizers and filter dyes can also be added to any intermediate or filter layers, or also to all layers to prevent excessive diffusion from layer -to layer with certainty.

In the same manner as described in application Serial No. 151,811, also compounds formed according to the present patent application can be added to the emulsion so that they are adsorbed as completely as possible by the silver halide grain, and the precipitation process may be repeated many times; if necessary, intermediate layers can be dispensed with. As the coupling leuco-derivatives are enriched and held in great concentration on the'silver bromide grain, one can rely upon this rather than on diffused distribution in the intermediate layers.

Thisprinciple is not limited to insoluble or slightly ,difiusing components, but is also gener- "ally applicable to other image producers of this kind and their salts from which the corresponding leuco-dyes are formed by oxidation, reduction or hydrolysis on the image, or generally diffuse before, after or during development, and it especially applies to the leuco-sulphuric acid esters of vat dyes.

- II. SYNTHESIS OF SPLITTIN G DERIVATIVES QF LEUCO-VAT DYES The intrinsic object was to find colorless or weakly colored or approximately complementarycolored derivatives of the vat dyes most stable to light, or of the colorful triphenylmethanedyes in whichthe auxiliary group needed for coupling could be simply and completely split off. In view of the extraordinary coupling ability of phenols, the tests were limited to those. derivatives in which especially 2-, 4- and fi-carboxylic acids and sulphonic acids of a-naphthol were used in addition to salicylic acid in the form of their chlorides; less often the chlorides of halogenated salicylic acids, halogenated mand p-hydroxybenzoic acid or halogenated naphthol carboxylic acids, amongst which are also considered the chlorides of ii-naphthol. The amino-derivatives of mand ,B-naphthol or their halide substitution products could, of course, also be used. Here, as well as in the coupling of insoluble or difiusionstable components mentioned in application Serial No. 151,811, the use of alkalies for fixing must be avoided, and the precautions previously, mentioned must be taken with acid methylene compounds, if solution even in weaker alkalies, such.

as, borax, trisodium phosphate, etc., is to be avoided.

A. HYDROLYTIC SPLITTING or Tm: COUPLING Gnome Ethers of the reduced indigoz'd and lignoz'd vat dyes, Zeuco-, indophenols and Zeuco-indamines The diethers easily prepared with dimethylsulphate,. chlormethylsulphate as well as the monoethers formed under certain conditions, especially I the monobenzylethers with the exception of dinitrobenzyl chloride are so stable to saponifying or oxidising agents that their use with non-hardened gelatine layers appears to be excluded. Esterification of thioindigo white with o-hydroxybenzyl bromide in the presence of tertiary bases, is also not very satisfactory, but better with nitrobenzyl bromide which, however, for easier coupling requires subsequent reduction and arylsulphonati'on of the amine obtained. Ether acids obtained by the action of chloracetic ester ac-.- cording to the German Patent 499,801 and British Patent 263,898, or their esters whose alcohol radical may be exchanged for any amino a-n'aphthol or its halide derivative, are easily split. Aryl ethers especially those formed with chlorodinitrobenzol, of which monoethers may also be prepared, as for example, that of leuco-pyranthrone, are relatively easily split by acid oxidizing agents. Coupling derivatives can be obtained with res orcin, aminoor nitro-phenols with subsequent reduction and arylsulphon'ylation, or by concentrating the diazotized amino-group. Triphenylcarbinol ethers of the leuco-vat dyes hydroxylated in a ring, are very easily decomposed by acids or Y oxidising agents, and also the leuco-vat dyes with German Patent 503,812, coupling groups can also be, combined with leuco-vat dyes of which -especially the lactic acidand glycolic acid ester are easily split (1337/3973). The condensation produ ts with acetone, etc., are also pointed out in this connection (German Patents 438,841, 281,998). Synthetic glucosides of leuco vat dyes and their generators (thioindoxyl, hydroxy-selenonaphthene, pyrogallol dimethyl ether, etc.,)

- corresponding to indican which can beprepared in the absence ofair, analogously to the methods used for the preparation of phenol glucoside, belong also to this group (349/2813, German Patent 593,422, French Patent 739,261, British Patent 405,195). Since these and the easily prepared acetone condensation products contain the same free hydroxyl groups, they can be esterified with coupling acid chlorides (of salicylic acid, a-naphtholcarboxylic acids, etc) the condensation products obtained are easily oxidised by oxidising agents. Triphenyl-chlormethane-p carboxylic acid chloride permits etherification of thio-indigo white (344/1627, 1619), whilst the acid chloride groupcan be permitted to act on any amino-a-na-phthol. It is worth mentioning that tribromphenol glucoside can be split much easier than the non-substituted compound; this holds also true for leuco-dye derivatives phenylisocyanite is advisable. Reduction takes (1149/2819) place after esterification of thioindigo white and 3077, 35/4200, 36/236, 39/930, Ann. 427/294, 301,

C. C. 1924, II, 2521, 1925, II, 190, etc.

In order to make the hydroxyl groups of indigo white and of other leuco-vat dyes stable and at the same time capable of coupling, the chlorides of salicylic acid, u-naphthol-2- or -4-carboxylic acid or -6-sulphonic acid, m-hydroxy-benzolsulphochloride or s u l p h i n o a c i d chloride (B.42/3814, 41/4114, 63/2818) dimethylaminobenzoylchloride (350/1045) are allowed to react in the presence of tertiary bases and with the exclusion of oxygen. Intermediate members could also be interposed and first esterified with chlorides of glycolic acid, lactic acid, aminoacetic acid, anthranil acid, etc., and then salicyllc acid, chloride, etc., allowed to react on the hydroxylor aminogroup. This, however, would result in products of higher-molecular structure, which are more difficult to wash out than salicylic acid ester of the simpler leuco-vat dyes. Esters with triazine-tricarboxylic acid or cyanic chloride in which one or two chlorine 'atoms are replaced by amino-a-naphthol, before group acylated with ptoluolsulphochloride.

The alkyland aryl-carbonic acid esters of indigo white and of numerous other leuco-vat dyes can easily be saponified by aqueous and especially alcoholic and dilute-alcoholic alkali or ammonia (German Patent 121,866, British Patent 235,247, 334/1858, 54/272, 55/2552, etc.), this is especially true for leuco-esters prepared with carbonic acid benzylester chloride (German Patent 556,798, 13.65/1192, which under certain conditions are split by catalytic neutral reaction. In the preparation of coupling acylating agents from salicylic alcohol, 1,5-dihydroxy-naphthalene, etc., the action of phosgene can be limited to a single hydroxyl group only when pyrazoloneor antipyrilchlorcarbonyl is used (German Patents 117,624/5, 118,356/7), which act first on the aliphatic hydroxyl group. They can also be allowed to react in excess with thioindigo white, etc., and the chlorformic acid formed with amino-a-naphthol, m-amino-phenol, etc., in the presence of tertiary bases so that the amino-group appears to be connected with the hydroxyl by a carbonyl group. It is less advisable to convert the amino-group of m-amino-phenol, amino-a-naphthol, etc., with the calculated amount of antipyrilor pyridinechlorcarbonyl into urea chloride and to let'this react with the alkali salts of leuco-vat dyes with air excluded, Under certain'circumstances, the detour via nitrated phenylurea chloride or German Patent 118,356)

the amino-group is arylsulphonylated. There is, however, the possibility of r e-oxidising the leucoform when using these derivatives containing nitro-groups, if the required amount of a suitable reducing agent is not present (359/1817, 1804). The action of phosgene on m-amino-phenol, etc., first forms an addition product which gradually splits off hydrochloric acid (British Patents 372,355, 377,278) forming urea chloride on warming the isocyanate. The isocyanates of naphthols can also be prepared via their carboxylic acid hydroxide (B.58/2850).

Ester acids are obtained with sulphochlorides of salicylic acid, a-naphthol-2- or -4-'carboxylic acid, which apparently contain a free sulphonic acid group (German Patent 264,786, British Patents 330,579, 337,846) and on account of their afiinlty to gelatine, cannot always be washed out without difficulty, but more easily so when using other combining agents for the halide. If the sulphonic acid group is in the p-position to the hydroxyl, it is split off during coupling; if p-amino-dimethylaniline has been used as developer, then the residual leuco-derivative can be removed with sodium carbonate or alkali and prolonged washing; if 4-amino-resorcin or similar ones have been used as developer, then the indophenol formed can be more easily eliminated than the residual leuco-derivative.

Esters with sulphonicor carboxylic acids of quinones are especially easy to split. Thioindigo white, etc., can be esterified with m-naphthol-4- or -2-carboxylicor preferably -sulphbnic acid chloride, also with phenol-por -o-sulphochloride; during the development with p aminodimethylaniline, the corresponding indamines are formed which are split by acid after the unchanged leuco-derivatives have been washed out with alkalies; the quinone residue is then split ofi in the presence of potassium ferricyanide or other oxidising agents or by acid in the presence of aromatic bases with formation of p-hydroxynaphthoquinone imides and liberation of the leuco-vat dye which is immediately oxidised. A similar reaction is observed in the esters with fl-naphthol-4-sulphoor -4-carboxylic acid chloride. The reduction products of the quinone derivatives mentioned can be added to the layers as insoluble developers, The corresponding derivatives of amino-phenols or amino-naphthols,

as obtained by esterification with diazoxide-sulphochlorides and subsequent reduction to oamino-phenol (German Patent 532,399, British Patent 401,643) are to be preferred, since the quinone imides formed are very easy to split, especially in the presence of oxidising agents.

The corresponding chlorides cannot be prepared from thio-indigosol and other leuco sulphuric acid esters of vat dyes, neither can they nor the esters be converted with amino-a-naphthols, or the like. However, analogous to the stable fluorideand chlorosulphonic acid esters of the simpler phenols, also those of many leucovat dyes can be prepared, and by their action on (methyl) amino-a-naphthol or preferably on aniline, a-naphthylamine, etc., coupling derivatives can be obtained in the presence of tertiary bases which easily produce hydrolysable indophenols with acid or alkali during development. The mono-chlorsulphuric acid ester of dihydroxybenzols can also be made to act on thioindigo white, etc., or the corresponding sulphurous acid chlorides, especially the hydroxylated benzyl de- Patent 331,842)

group or its bromo-derivative.

- r to reform the dye may be used to advantage for vat dyes, the corresponding o-hydroxybenzylsulphuric acid esters could also be prepared. Analogous to the usual sulphuric acid esters, the

esters of thioindigo white and of other leuco-vat dyes can also be prepared in the presence-of tertiary bases, with 'chlormethylsulphuric acid chloride which is rather capable of resisting lye- (360/2292). The chlorine atom 'can be converted with amino-a-naphthol in the presence of natural copper. Ring formation during the action of phosgene or other acid dichlorides can best be prevented, if leuco-vat dyes are used for esterification with hydroxyls which are widely separated from one another, as for example, violanthrone, pyranthrone, and the like, or partially reduced vat dyes with only one hydroxyl group as they exist in the dihydro-compounds of flavanthrene and pyranthrone (344/1452, 51/443, 59/1830, British prepare first the mono-esters or monoethers of leuco-vat dyes with two hydroxyl groups, which are then converted with the coupling acid ch rides; the mono-sulphuric acid esters of indigo white and thioindigo white can also be regarded as such.,

On the other hand, one may intentionally Work towards a formation of rings during esteriflcation by esterifying thio-indigo white; for example, with the dichlorides of nialonic acid or methionic acid; an amino-group, present in the acid methyl group which may also be added later, is used for esterification with a-naphthol-2-carboxylic acid chloride or sulphonic acid chloride; a chlorine or bromine atom already present is used for conversion with amino-a-naphthol or m-aminophenol, etc. Energetically acting developers can, however, also couple with the acid methylene The reduced azomethine derivatives of the leuco-vat dyes formed outside the emulsion can be added to the layers as leuco-developers, which yield the corresponding indophenol derivatives even with sodium carbonate.

The esters and ethers of the anthranol form of acylaminoanthraquinones (British ,Patent 340,983, German Patent 567,845) as well as the mixed esters of the anthrahydroguinone form (German Patent 543,028) which can usually be easily saponified by alkalies, especially in the presence of oxidising agents andalso when using u-naphthol-carboxylic acid chloride, .etc., are of special importance.

In certain respects, also the ether acids formed from thioindigo white, [3-tetrahydro-flavanthrene, etc., with chloracetic acid. chlormethane sulphonic acid, and the like, belong to this group and can be converted into the chloride which is in turn converted with amino-u-naphthol (German Patents 414.426, 499,801, 502,044, British Patent 263,898, BAG/3366).

B. SBLITTING or THE (loUPLINo (moor avv OXIDATION -For theoretical reasons and because of the great resistance of the gelatine to oxidising agents, it was found that a perfect, liberation of the original vatdye by a cold method is best possible by destruction of the coupling group ,by oxidation, or better expressed, of the intermediate member connecting the same with (leuco) dye.

,The strong tendency of thio indigo white, etc.,

Another procedure would be to the elimination of acyls, etc. It was mentioned several times in the examples of the previous chapter that the presence of an oxidising agent is very helpful for liberation of the (leuco) vat dyes from their esters and ethers. The more easily oxidisable insoluble (or at least not appreciably diffusing) esters and other derivatives of leuco-vat dyes, or their intermediate products without an attached coupling group, which'are described later, can, of course, also be added to .the layers for catalytic purposes, instead of' the insoluble indigo salts for image or diffuse oxidation. This is also claimed as subject of the invention. Coupling derivatives of the (leuco-) .vat dyes concerned are classified by the oxidisable intermediate member connecting the (leuc'o-) dye with the coupling group.

(1) Carbamic acid derivatives The carbamic acid-, allophanic acidand biuret carboxylic acid esters of vat dyes are the most suitable of the compounds concerned, since they are split by dilute alkalies, even when cold, and also slowly by barium hydroxide solution, and are destroyed through oxidation by hypochlorite and acidified nitrite solution. These products are obtained from the dry leuco-bodies dissolved or suspended in chlorobenzol, carbon tetrachloride or other organic solvents by the action of one or two molecules of urea chloride, allophanylchlo ride or biuret carbonic acid chloride in the presence of tertiary bases, if necessary, with moderate heating (German Patent 238,961, British Patents 423,864, 436,657, 439,380, French Patents 769,709, 785,458, 790,454, Add. 46,196 and 769,920). When excess phosgene in pyridine solution reacts with bis-urethane; bis-chlorformyl urethane of the thioindigo white is first formed; with a small amount of phosgene, ring closure to cyclic carbonyldiurethane results (C. C. 1897, II, 25, 3.39/687, 26/2173, 19/2344) or chaining of two molecules of carbamic acid ester in the monoacyl-', mono-benzylor mono-phenyl derivatives, or intheanthraquinone vat dyes reduced to the anthranol form of the algol type, etc. All these products or their insoluble salts may be added to the layers without fear of fog with alkaline earths, copper, cadmium, zinc, etc. Analogous ring formations appear to beformed from the bis-carbamic acid esters of leuco-vat dyes; also- 26/2173, 28/2383, 36/739, 38/297) easily react I with chlorides of salicylic acid, m-phenol sulphonic acid (343/2486)a-naphthol-2-carboxylic acid, 4- and fi-sulphonic acid, fi-naphthol-4-sulphonic acid, and the like, in the presence of tertiary bases and of organic solvents; also with cyanuric chloride, whereby the third chlorine atom is exchanged for amino-a-na'phthol. The acyl derivatives obtained couple also in the insoluble or not appreciably difiusing state, or in the sulphonylldes in the form of insoluble salts with or ganic or inorganic bases, preferably in the presence of sodium carbonate or still weaker alkaline reacting substances, since solution often takes place with fixed alkalies (328/2383, 35/781) and the ac'ylated. urethanes are transformed into ureas by dilute ammonia with liberation of the leuco-vat dye.- The same applies to as easily destructible.

the condensation products of amino-a-naphthol, etc., with the chlorformyl derivatives of the carbaniio esters of thio indigo white and its monoacyland mono-aryl ethers, as well as of the acylamino anthraquinone dyes reduced to the anthranol form, or of their mesoanthramines which can easily be prepared with an excess of phosgene. The anils of the carbamic and allophanic acid esters prepared by combination with salicylic aldehyde, a-naphthol-2-aldehyde or with other coupling aromatic aldehydes are somewhat more difiicult to re-oxidise.

Similar to the carbamic acidand allophenyl esters in their behaviour are .not only their hitherto-mentioned acyl-, but also their aryl-derivatives, as they can easily be prepared by the action of phenylurea chloride on thio-indigo white or its carbamic acid ester in the presence of tertiary bases. Hydroxylated derivatives suitable for coupling purposes are not very suitable and are difiicult to prepare, giving only a poor yield, regardless of the positive assertions of British Patents 372,355 and 377,278, since self-esteriflcation takes place very easily, unless the 2-position of the a-naphthol is occupied by the halide or the carboxylic acid aniiide group, or the 6- halide-salicylic acid anilide is used which may also contain the amino-group otherwise provided previously mentioned, by splitting the azo com-- bination after esterification by reduction (German Patent 242,291) and by arylsulphonylation of the diamine formed.

(2) Dicarborylic acid derivatives The coupling residue can also be combined with hydroxyls of leuco-vat dyes by other dibasic acids instead of by carbonic acid. Here,

. however, only oxalic acid, sulphoacetic acid and possibly also methionic acid can be considered The semi-chlorides corresponding to oxanilic acid and malonanilic acid can easily be prepared by means of thionyl chloride (3.64/26, 54/1215). The chloride of a hydroxylated oxanilic acid can be allowed to act on thioindigo white, or the latter may be allowed to react first on oxalyl-chloride followed by any amino phenol or amino-a-naphthol; the semi-chloride of malonic acid serves similarly for esterification of the leuco-form and the product obtained is converted into the chloride according to British Patent 401,643, or with thionyl chloride. The dichloride of dicarboxylic acids mentioned can also act with ring formation, and the acid methylene group can couple with an energetically acting developer to ammethinzs which are decomposed by acid in the presence of an oxidising agent. All these'substances form nitroso-bodies with acidified nitrate soluion analogous to NO-phenylurethane or NO- acetanilide (B.42/3582, 28/2375, 10/960, Ann. 325/22C) from which the leuco-vat dye or its ester is liberated with dilute lye or sodium carbonate, phenolate or sulphite solution. This acid ester can be further liberated by the presence of hydrogen peroxide or acid potassium ferricyanide to the dye' oxydising ester acid. Two molecules of chloracetic acid or chlormethane sulphonic acid can be made to react with m-amino-phenol, converted into the dichloride and this allowed to react on thioindigo white. In the remaining residue of the latter, (the indiphenol or the quinone formed from it by acid) the p-position is nitrosated to the dimethylamino group, or after first general development and removal of the residual derivative, it is bathed at once in acidified nitrite solution and NO-phenol is split off by lye. The diamine formed is easily oxidized to the vat dye. Carbamic acid ester can be used instead of the leuco-vat dye in all instances given.

(3) Monocarboxylic acid derivatives 52/813, 54/287, 41/3360). Thioindigo White, etc.,

can also be esterified with chloracetyl chloride or chlormethane sulphochloride, and the chlorine present in the methyl group can be converted with sodium salicylate acid, phenolsulphonic acid salt, etc.. or preferably with mor p-amino-phenol amino-a-naphthol, also a-naphthol carboxylic acid amide or phenolsulphamide or with their alkali salts in the presence of native copper, or

the like, in order to obtain coupling compounds comparable to hippuric acid esters (3.41/2880, 46/2369) which, like these, are split with varying facility by acidified nitrite solution or other oxidizing agents (339/1373, 58/1352). The same products can, of course, also be prepared by direct esterification of thioindigo white with coupling compounds having a structure analogous to hippuryl chloride as they are easily prepared from amino-a-naphthol or its 2- and 2,4- halogen derivatives or from salicylic chloride,

etc., and glycocoll, oxymethane-sulphonic acid,

(4) Substituted carboa ylic acid derivatives The phenolor naphthol group can generally be combined with reduced vat. dyes by intermediate members containing one or more or some of the .various following groups: ethylene compounds, hydroxyl groups, ketoneor sulphonic groups, carbamide, or urea groups, the acid methylene group or other substituents which are easily attacked by oxidising agents. In addition to this they may contain a terminal sulphonic acidor carboxylic acid group which latter is converted into the acid chloride directly or after preliminary masking of the alcoholic or phenolic hydroxyl'groups with thionyl chloride .or phosgene in the presence of tertiary bases. The very easy destruction of these compounds by oxidation with liberation of the vat dye indicates their usefulness; A few of .the known substances from the endless known source, or those which can be prepared by organic synthesis from the methods outlined, are: o-hydroxy-cinnamic acid (B. 46/3257, 3284) hydroxylatedmandelic acids (B. 14/1317, 17/974) o-hydroxyphenyl lactic acid (B. further hydroxy-derivatives prepared analogously to benzylsulphochloride (B. 39/3313, 42/3814) or to benzylthioglycollic acid or to the sulphone pre- Derivatives having a coupling acid methylene group The esters which contain a coupling acid methylene group are noteworthy, since these themselves are not only easily destroyed by oxidation, but also the azomethines formed during coupling developing with p-amino-dimeth-.--

yl-aniline, etc., these are easily decomposed by acids or alkalies, generally with temporary formation of very unstable triketo-esters, similar to NO-compounds formed by acid nitrite solution (B.34/3047, /1437, 3307, 37/1526, 40/664, German Patents 109,486, 116,089, 117,627, 121,745, 3.42/2746, 3188) Higher molecular vat dyes in which the acid methylene group of the acyl residue forms no soluble or appreciably diffusing or immediately dissociating salts with'the weak alkali, necessary for development, are not suitable.

The methylene group may-also be brominated and treated with the same precautions for coupling of insoluble components as in application Serial No. 151,811.

Similar coupling esters are not only obtainable from leuco-vat dyes, but also very easily from their carbamicand allophanic acid esters by means of cyanoacetic acid chloride (365/436) in thepresence of pyridine, also from the diester of thioindigo white with chloracetyl chloride or chlormethane-sulphochloride by conversion with potassium cyanide, nitrite, etc., or also in the presence of copper salts; Analogous ethers are also prepared by w-chloracetyl-nitrobenzyl cyanide'obtained analogously to the nonnitrated compound (341/3046) Malonic ester' acids of leuco vat dyes (British Patent 317,428) or their esters or anilides prepared with malonic ester semi-chloride or malonic acid semi-chloride (340/2211, 46/2201) as well as those of their carbamic acid esters, are suitable; further, the esters with m-ethionic acid, sulphoacetic acid, etc., analogously prepared. On the or Cl group catalytically or by means of hexamethylene tetramine, etc.,,to the ketone group. Coupling esters with pyrazolonc carboxylic-or acetic acids or their chlorides are also easily prepared (B.35/1437). Esters obtained with the semi-chloride of malonic acid ethyl ester can be converted by exchanging the alcohol residue for amino-a-naphthol, It is less practical to make malonic acid semi-chloride react first with amino-a-naphthol, to re-convert into the chloride and then allow. it to react with-thioindigo white. -An aminoor halide group can also be introduced into the acid methylene group and this converted with a-naphthol-2-carboxylic acidor sulphonic acid chloride or with aminoa-naphthol or m-amino-phenol, in order to obtain coupling groups more rapidly. It would, however, be a' round about way to esterif thioindigo white with a hydroxylated arylazoacetic acid chloride (German Patent 477,450) and to remove the residual ester after development coupling' by lye, then to split the azo-compound by reduction and to re-convert the amide-acetic ester derivative generated by oxidation-into the vat dye. In all derivatives having an acid methylene group, condensation with NO-phenol or NO-u-naphthol could also take place outside of the emulsicn,-the NQ-group being in meta-position or in the second nucleus-, and this ammethine could be added directly to the layer before or after reduction. The residual ester is eliminated by lye after alkaline coupling with sodium carbonate, the indamine split by acid and simultaneously oxidized, if necessary, in the presence of phosphotungstie acid in order to pre vent diffusion. The cyclic esters formed by the action of methionyl chloride, sulphoacetic acid di-chloride in the presence of tertiary bases,

where both hydroxyls of thio indigo white are esterified by one molecule of these di-acids, deserve special mentioning, since they behave exactly as the compounds previously described; also the cyclic compounds with an acid methylene group prepared in the same manner from bis-' carbamic acid esters of leuco-vat dyes.

(6) Phosphoric acid derivatives products obtained can be converted with aminoa-naphthol or m-amino-phenol, etc., also with other hand, esters with aceto-acetic acid can only be indirectly prepared, by first allowing 5- hydroxy- .or p-chlorbutyric acid chloride to acte its 2-halide derivative, and then only allow this dichloride to react with the leuco-vat dye in the presence of tertiary bases. During esterification of thioindigo white, etc., with only one molecule of phosphorus hydroxy-chloride, etc., formation of-ring systems probably takes place, as they are prepared from pentavalent phosphorus even with o-diamines (358/848, 2144) and are known from trivalent phosphorus with pyrocatechin (B.27/2558, 59/2848), As the derivatives of the latter are much more easily decomposed by acids and alkalies with liberation of phenol, and this also applies to phosphoric acid-, alkayl-phosphoric acidand phosphorous acid esters of leuco-vat dyes (German Patent 489,725, British Patents 333,506, 260,647, 248,802, Swiss Patent 123,738), therefore, the use of the latter is recommended for synthesis of coupling derivatives by exchanging the third chlorine atom for aminoa-naphth'ol, m-amino-phenol, etc., (358/2156, 27/2569) because the thioindigo white compound which, similar to di-pyrocatechin phosphoric acid mono-chloride, is readily split and exchanges its chlorine, can be prepared only with difliculty, even in the presence of tertiary bases. The derivatives-of pentavalent phosphorus mentioned can, however, also be directly reduced to those of phosphoric acid during the preparation or after coupling development. The derivatives which correspond, to phosphoric ester (B.60/295, 59/1120, 58/661, 57/102, 1023) in which, under certain conditions, one-sided saponification can take place with cold lye or the coupling products similarly prepared with phosphorus nitrile chloride, are less suitable (360/160, 57/1343), A way round this difliculty would be to prepare the more readily oxidized analogous amino derivatives of carbamic acid esters from leuco- Most of the derivatives previously mentioned can also be prepared from generators of vat dyes, as for example, thioindoxyl, hydroxy-selenonaphthene, pyrogallol dimethyl ether, etc., but it is usually diflicult' to split or reoxydise them to the vat dye. Coupling o-esters of indoxyls and especially of N-methylor N-phenyl indoxyls and of phenyl-oxy-thiophene (345/3393) are not onlycapable of being saponified by themselves with sodium carbonate or acid (3.57/246, 55/1600, 45/2075, 2280, 3393) but like the o-ethers, they are even more readily saponified after previous nitrosation of the imino-group (3.15/781, 16/2190) which may be done on the image individually or collectively. The coupling N-acyl derivatives are not sapo'nified by alkali after the image treatment, but only after oxidation to the indigo dye (German Patent 108,761).' The corresponding acyl derivatives of amido' thionaphthene behave in the same manner (Ann. 351/412) and also those of hydroxy-thi'onaphthene-quinone-a-lmide (CC. 1932, I, 389).

Furthermore, indoxyl and the generators of other vat dyes could be combined with salicylic aldehyde, etc., by means of glucose, mannite, etc., to indican-like compounds which are split by acid oxidizing agents similar to the known non-coupling glucoside of indoxyl (B. /4338) (CC. 1923, I. 1628, Chem. Ztg. 1981/7613,

1145/2467, 49/2813, 17, German Patent 593,422,

British Patent 405,195, French Patent 739,261, and 47/1214, 49/1644, 52/854, 60/1350) and which are made more easily soluble in water by the introduction of sulphuric acid groups (3.58/886, 38/1860). Tetra-acetylbromoglucose'can be converted with indoxyl, and the aldehyde group newly produced at the other end of the chain can be allowed to react on amino-a-naphthol. Coupling acid chlorides may not only be allowed to react directly on a hydroxyl group, but also on an amino group introduced with alcoholic ammonia or on the arylsulphonyl derivative (13.58/295, 300, 48/268, 52/816) or the suitable use of the acetone derivatives of sugars. In glycuronic acid or its acetoneor acyl deriva tives, the aldehyde group can be combined with the indoxyl residue, and the carboxylic acid group by means of its chloride with amino-@- naphthol or m-amino-phenol. Or the reverse may be done, in which case it is best to allow salicylic acid chloride to react first with hydrazine, and the hydrazone formed then combined with the aldehyde group, the carboxylic acid chloride group combined with indoxyl, and finally, the acetone residues or acyls removed.

0. COUPLING 1\IES()-DERIVATIVES or ANTHRAQUINONE DYES Owing to the special relationship of the two centre carbon atoms to each other in the anthraquinone series, an essentially greater variety of methods for producing coupling derivatives is possible than with indigoid dyes, mainly because in compounds with several quinone groups, the more or less complete reduction may be extended to all or only a part of them;

Ethers and esters of the anthrahydroquinone form behave exactly like those of the vat dyes previously described. They difier from those of the vat dyes, however, in that they show a. much stronger individual color. It is obvious that here also, coupling groups can be introduced with salicylic acid chloride, hydroxy-benzyl chloride, etc.

On the other hand, the analogous derivatives of the mono-valent anthranolor anthranylmercaptan form (German Patent 567,845, British Patent 340,983, Ann. 420/1, 340/518, 46/29, 47/2997, 55/3970, 45/2965) are more easily prepared on account of their greater stability, but they are more diflicult to re-oxidize, with the exception, perhaps, of carbamic acid esters, etc., as well as their coupling acylation products, both of which are easily oxidized by acidified nitrite. Compounds of meso-anthramine, or its substitution products with a-naphthol suiphonicchloride or a-naphthol carboxylic acid chloride and other coupling acyls, can be regenerated still more readily to the corresponding anthra-quinone dye. Anthranol and mesoanthramine, or its aryl-sulphony] derivative, also couple directly in solution; for example, with diazo-compounds or NO-dimethylaniline (BAG/518, 528, 58/829, 48/1720). Coupling of the most finely divided insoluble compounds, however, to the meso-indamine during development with p-aminodimethylaniline and sodium carbonate is much too slow, unless the anthrone form is brominated in the meso-position. The reduced condensation product could, of course, also be added to the layers as leucodeveloper with NO-dimethylaniline or NO-phe- 1101, also that of meso-anthramine. Since the coupling products are split to anthraquinone, with 1% cold or slightly warm alcoholic hydrochloric acid solution (BAD/525, 528) which also applies .in substitution of the nuclei by amino-, dimethylamino, acylamino-, hydroxyand sulphydril groups, this ofiers a convenient way of regenerating the leuco-anthraquinone dyes added to the layers, but the introduction of bromine,

however, is diflicult. The condensation product and thelike '(B.58/978, 64/2185, 1569, 65/1301) only in the presence "of negative substituents. Dehydrated 9-anthroxyl-chloride and anthracene-9-acetyl chloride (344/202, 47/480, 58/1619) as well as its 10-halide derivative, react readily with m-amino phenol or amino-a-naphthol.

Q-anthroxylamine and 'anthracene-9-acetamide also react in the presence "of tertiary bases with coupling acid chlorides. The halide of mesa-wchloracetylanthracene easily'exchanges its halide for coupling residues; it is also converted by KCN to formation of the coupling acid methyl compounds (German Patents 547,644, 536,652, 552,269, 1856/2360). T h e Q-anthrone-actic a c i d (13.56/ 1619) can be transformed into the chloride and converted with m-aminophenol, etc., 9-anthrylamine and 9-anthrylmercaptan alsoreact easily with chloracetic acid, and the corresponding chlorides are converted with amin'o -naphthol, etc., (B.55/3978). In all these products which are, of course, substituted by amino-, acylaminoand similar groups, the meso-group is removed by oxidation with acidified nitrite or stronger acting oxidizing agents with formation of the dye (318/3170).

The meso-methylene group of vat dyes reduced to the anthroneform is relatively easily condensed with coupling aromatic aldehydes, often prepared Without difiiculty, as for example, salicylic aldehyde or a-naphtholaldehyde (B.41/ 1037, 55/228). These compounds are usually reoxidized to the anthraquinone dye even byas mild oxidizing agents as 1% hydrogen peroxide or persulphate in the presence of alkali or sodium carbonate, or by acid oxidizing agents (B.54/2328, 59/767, Ann. 418/30, 420/134, 13.16/703, Ann. 307/213, 0.0. .1900, II, 655, 334/222, 46/29). These hydroxylated coupling .benzol derivatives of the anthrone form can also be obtained with concentrated sulphuric acid from hydroxy ixanzyl-oxanthrones which, in turn, are readily prepared by benzylation involving reduction with zinc powder and lye, or with the aid of hydroxybenzyl chloride or hydroxylated leucotrope (Bill/2152, 42/1575, 47/1055, 1271) with bridge formation by splitting oil water. The monobrombenzol anthrones prepared from their dibromides by splitting off hydrogen bromide can also be easily reoxidized, as can other compounds 'obtained from it, 'by exchanging the bromine atom for coupling molecules (323/2529, 47/1057,

Preparation of coupling meso-azo compounds from anthranol or meso-anthr'amine is more complicated (13.40/518, 46/29, 48/1720), because, in this case, the coupling group would have to be split off by reduction and then oxidized .to the anthraquinone dye, since splitting by alcoholic hydrochloric acid solution is not easy. Complete reoxidation of tetraand octohydrated anthranol-azo bodies, or those substituted by aminoor acylamino groups, is just as diflicult (B.5B/2677, 79, 83, 93, 96)

Conversion of meso-carbon atoms leading to coupling derivatives can often be eflected, in the case of finished vat dyes, if they contain stable chromophore groups of which acylamino-, dimethvlarninm, arylaminoor 'nitrogroups are examples. In other cases, they are prepared later by reduction or acylation from the nitro-groups present; or one may start with condensed higher nuclei which themselves have dye characteristics as in the case of naphthanthraquinone. The anthrone form is either partially or entirely prepared with higher anthraquinonazine dyes (indanthrene, flavanthrene, etc.,) or more simply with vat dyes, where one or more anthraquinone nuclei are condensed with indigoid nuclei. In reduction to the anthrone form the indigoid component of the dye is reduced, but it readily reoxidizes itself in air, unless the vat-hydroxyls are converted into leuco-sulphuric acid esters analogous to indigo-sols. When these ester acids are added to 'silver halide gelatine emulsions in the form of insoluble salts, the indigoid component is best re-oxidized by very mild oxidizing agents after first general development in the presence of acid, which splits oil sulphuric acid groups, and followed byc'oupling development and combination with the coupling group attached.

Reduction of the simpler anthraquinone dyes is not always necessary, since its anthroneor anthranol form can oiten be easily prepared by condensation of correspondingly substituted o-benzoyl-benzic acids (Ann. 307/313, Q0. 1900, II, 655, German Patent 112,297).

The indophenols, etc., formed outside the emulsion by condensation of the coupling derivatives with p-NO-dimethyl-aniline or p-NO-phenol can always be reduced and added to the layers.

- The foregoing also applies for the substitution products of diphenylmethane sulphone constructed similar to anthro-ne (BBB/965) D. COUPLING 0- AND N-ACYL DERIVATIVES or Hrmmzo DYES It is known that ethers and esters of hydroxyazo dyes are relatively easily split by alcoholic gration of the acyl groups towards a nitrogen then removing the coupled compound in the imatom of the hydrazo group takes place, although the insolubility in dilute alkali is evidence to the contrary (8.38/1100, 1105, 40/1433, 2155, 41/990, 40 6, 418, 48/1701). The benzoyl group attached to the hydrazo nitrogen is split off onlyv during re-oxidation in'the presence of lye (338/1113); in other cases, however, a migration towards the hydroxyl takes place (15.40/ 2156, 41/990) A similar re-arrangement of acyls also takes place in many o-aminophenols and o-arnino-benzyl alcohols (337/2250).

This then makes it possible to acylate the one nitrogen atom of the hydrazo group with salicylic chloride, or the like, in order to obtain a sutficiently stable product which may be added. to the layers without harm. Alter coupling and age by a developer containing sodium carbonate, the insoluble azo dye remaining in the image can be regenerated, by oxidizing agents in the presence of sodium carbonate or other suitable alkalles. The hydrazo forms of the ether of hydroxy-azo dyes or'aminoazo dyes may be used for this purpose. Even if coupling acyl esters of hydroxy-azo dyes are added to the layers in a reduced form, a. re-formation of the dye in the presence of alkaliesoccurs by the action of oxidizing agents which split oil! the acyl group with out solution of the o-azo bodies. The corresponding m-azo dyes are more suitable than or p-hydroxyand amino azo dyes, since their hydrazo forms are essentially more stable. (8.5/480, 30/2939, 36/4112, 45/596, 1152, 46/824, Ann. 425/141, 427/142-221, 426/76-121, C. C. 1934, I, 755).

E. COUPLING DIAZO-AKINO- mp aso Conrounns The coupling group can also be connected by a diazoaminoor are compound with the genuine dye or its leuco-iorm; the former is split by hydrolysis with acids, the latter by reduction (3.25/ 1347, German Patent 410,310, British Patent 377,024, German Patents 268,779, 229,267. 282,890, Ann. 443/216). Dyes with one amino group, as for example, aminobenzanthrone, aminoindanthrene and other amino-anthraquinone dyes, also amino-azo dyes or leuco-triphenylmethane dyes with a free amino group, are combined with a-naphthol-4-sulphonic acid containing a diazo group in the second nucleus to form the diazoamino compound, and added to the layers as insoluble salts. During the development with p-aminodimethylaniline an insoluble indamine derivative is formed by replacement of the 4-sulphonic acid group; the non-coupled diazoamino compound is washed out with sodium carbonate or in and is the genuine image dye liberated by acid from the indamine. 4A diaso-anaphthol could also be used, especially when during development with p-amino-salicylic acid, amino-resorcin, the compound will be washed out at the exposed places and the residual diazoamino compound afterwards decomposed by acid.

- Any 2,4-dihalogenated amino-a-naphthol, can be diazotised and combined with correspondingly substituted amino-thioindigo or its leuco-sulphuric acid ester to form the diam-amino compound oi bisdiazo-amino compound, or coupled with hydroxylated vat dyes or their leuco-esters highly-halogenated compounds, in spite of the data oi German Patent 245,281, Ann. 443/216) or its leuco-sulphuric acid ester, etc., could also be combined to the azo compound with one molecule of 2,4-dihalide-a-naphthol by means of a hydroxyl group in the second nucleus thereof, or by means oi an amino group substituted in the oand p-position to a diazoamino compound.

Further, a highly halogenated diazotised aminothioindigo can be combined with resorcin and coupled at the latent image to the indamine, and

- the residue of the compound in the image, sp.it

to the azo compound. Alter coupling development or splitting oi! any sulphuric acid residues by oxidation, etc., the dye derivative residue in the image is hydrolyzed by acid in the former procedure. and in the latter the coupling auxiliary group is best split oil by acid reduction of the azo compound. This is especially easy with 539,331, 545,714, 583,315, 540,619) on the other.

hand, yield genuine phenylhydrazone compounds which are coupled oil'during development with p-amino-salicylic acid, amino-resorcin, etc., only in the places containing silver, whilst the residual azo-body is split by reducing agents containing sodium carbonate or by vigorous catalytic oxidation, and the residue oxidized to the dye. Analogous derivatives of azo-indoxyl (C. C. 1923, IV,

866) are less suitable. A resistant yellow dye is added to the upper layer which can be coupled 01! against the reagents otherwise necessary here.

to aminothioindigo by reduction. The known thioindigo-asodyes and their stable reduction products may also be used for the present pur- (Ann. 443/216, 220, German Patent 245,281.) Additional intermediate members may also be interposed in all these cases. by first allowing anthraniiic acid chloride, azido-acetic Y acid chloride or nitro-benzoyl chloride to react with the leuco-vat dye followed by reduction, and treating these new "amino-compounds as suggested. So far as the new groups show aliphatic character, they are combined in the usual manner with diazotised amino-phenol or amino-anaphthol to diaso-amino compounds which couple during development. It should be mentioned that certain diam-amino bodies are stable even to alkaline hydrosulphite and other reducing agents (German Patent 268,779, 3.35/2065. /1144, 46/1529, C. C. 1932, II, 525).

F. Acmrxmooumons Leuco-dye sulphochloride is allowed to react with aniline, etc., and the sulphamide of the dye is liberated by dilute acid from the indamine derivatives formed during coupling development (Austrian Patent 101,004). Also the combination with mor o-amino-phenol is suitable (J. i. pr. Ch. (2) 51/435-43, German Patent 128.815). The chlorides oi leuco-dye sulphoor carboxylic'acids or of their generators and those of thioindoxyl and thiolndigo r act readily with amino-phenols, 2-amino-a-naphthols, etc. 'lhe sulphamide oi. the dye is liberated aiter'development coupling by acid oxidation. Also the ordinary (thin)- indosyl-carboxylic acids, etc., or their esters may be used to prepare analogous p-aminophenol desiyvztives which are oxidized by acid to the vat G. Comma Airing Even though many anils oi the aldehydes and ketones are relatively easily split by acid or lye.

(325/2754, 27/3009, 28/208, 81/2252, 32/1684. 33/800, 34/3050, 35/359, 375. 918, 3310. 36/3221, 3233. 37/1904. 42/2108. 3632. 43/603, 2478. 45/2915, 46/2270, 3721, 47/1863, 48/1482, 50/89, 53/340, 54/3125-42, 58/818. 59/848. 2887) this is less pronounced with those which are especially suited for coupling oil, as they are iormed, forexample. by condensation oi salicylic aldehyde or e-naphthol-2-aldehyde, salacetol. 2- 0l' 3- aceto-a-naphthol (3.21/636, 28/1947, 48/28, 1703. /753, 56/1308) with leuco-dyes containing one amino group (German Patents 256,761, 238,982,

B.45/2236). Possibly the best reacting compounds are the derivatives of aceto-acetic acid or its anilide derived compounds with amino dyes;

their coupling ability, however, is not very great. The corresponding dye derivatives of acetylacetophenols and -nal1hthols are better suited (858/2537, 38, 60/1085, 93).- Bince these prod- On the other hand, one molecule of the diazotised amino thioindigo (which is possible with note are constructed like p-aminocroionic acid ester (Ann. 439/214, 3.60/1827, 59/2548, 42/3912.

25/776) which can be readily split, chlorides oi w-chlor-substitution products and, possibly, also with formimino compounds of phenols and acetic acid derivatives (3.58/818).

2-anils of isatin, thionaphthenequinone, seleno-naphthenequinone, etc., excel in their ability to split easily (B.47/2300, 43/1371, 77, 42/4278, 45/155, 159, 44/341, German Patents 113,980, 115,465, 241,623, 354,455) and they are also partly soluble in bisulphite. Analogous to German Patent 241,623, coupling 2-derivatives can be obtained with m-aminophenol and amino-a-naphthol; after coupling at the image, the vat dye can be liberated from the residue of the compound remaining in the image by ammonium sulphide or hydrogen sulphide (3.43/1384, German Patent 175,423, 58/821). The red-violet 6,6'-di chlorindigo' is used for the purple component image. The ability of the isatin-a-anils to split by hydrolysis or reduction permits a very interesting use thereof. A hydroxyl'group can be introduced into the phenyl group of the isatin, or the isatin of hydroxy-phenylcan be prepared, and from this a-anils with amino-(leuco) -dyes.

The residue remaining on the image is split by dilute alcoholic hydrochloric acid solution liber ating the amino dye.

Similarly, some a zomethines of imide are easily decomposed (C. r. 153/531). A molecule of a dye containing a NO-group could be condensed with its derivatives substituted by hydroxyl or with 2-acety1-aceto-6-methylphenol in order to obtain coupling products during development from which the dye can be liberated by acid. These nitroso-derivatives of dyes which are most easily prepared by oxidation of an amino group, can also be allowed to react with dehyde dye by dilute acid or in the form of the oxime or phenylhydrazone (3.27/3005, 59/848, 756). Indoxylaldehyde or thioindoxylaldehyde (57/650, 44/3100) can also be condensed with p-- aminophenol; after coupling, the vat dye is then formed by oxidizing agents, especially acid nitrate from the residue remaining in the image. For the upper layer a yellow coupling dye is chosen which is stable to oxidation. and maminophenol are also suitable, especially since homophthalthe latter is nitrosated and oxidized by this and a negative nitrogroup favours splitting of the anil.

HI. SPLITI'ING DERIVATIVES 'OF NON- REDUCED DYES 324,119, 13.56/34, 57/647, 59/1822, 62/2165.- By the action of salicoyl chloride, naphthol-sulphochloride, etc., on dyes or their N-carbamic acid esters the usually red diand also. blue monoacyl derivatives are easily obtained by coupling or then dissolving off in the presenceof sodium carbonate, whilst the residue of the combination remaining in the image reforms to the original indigo dye with dilute alkali or ammonia, if necessary, with gentle warming. The generally weakly colored bisulphite addition products and their leuco-sulphuric acid esters which, however, must be added to the layers as insoluble or at least not'appreciably difiusing salts with organic bases, show a similar behaviour. The N-acyl compounds must be regenerated from them before coupling.

C-acyl derivatives with salicylic acid esters or other acyls on the two middle carbon atoms which are easily oxidized 017, may be easily split by dilute acids, but they are of little practical importance on account of the difficulty of their (Trans. Ch. Soc. Vol. 125/878,

by hydrolysis or oxidation, can also be obtained like the corresponding derivatives of leuco-vat dyes dealt with in previous chapters. Under certain conditions, and when the dye is sufiiciehtly resistant to oxidation, they may be prepared from dyes with amino-groups, such as aminoanthraquinone, amino-indanthrene, am i no thioindigo, etc. chloride (BAG/2201) can be allowed to react with this or with the indol-nitrogen of indigoid mixed dyes, or also cyanide-acetyl chlorid (or chloracetyl chloride followed by phenolsulphamide), since ketonic acid esters formed during hydrolysis of the azomethines produced are especially unstable to saponifying and oxidizing agents. The products obtained with oxalyl chloride and amlno-u-naphthol are also easily destroyed (BAH/1131, 54/1215). Coupling acyl derivatives could also be prepared from indigo-monoand -diimide (346/1694, 2260,57/240) or also from NN'-phenyl-hydrazine-indigo (352/533). With these, however, the vat dye is-regenerated with greater difficulty by hydrolysis or reduction.

Still less so the dianilide (342/3640) formed color, is liberated with dilute acid or in the presence of oxidizing agents (B.39/ 1560, 34/3479, Austrian Patent 101,004). The reaction prodducts of two molecules of the dye sulphochloride with 1 molecule of aniline, a-naphthylamine, mor o-aminophenol, etc., are less suitable as coupling bodies.

DialphyZamines.-Two molecules of a dye containing a benzyl-chlorideor alkyl-chloride group can be allowed to react with aniline, a-naphthylamine, etc. This product couples only with diniculty; however, the bis-amino dye can be split from the indamine by the action of strong alkalies. A combination with mor o-aminophenol, 5- or 8-amino-a-naphthol could be effected, then remove the residue with lye after coupling to indamlne, nitrosate and split with lye (3.18/2918, 35/3035, 37/44, 46/953, 960, 48/1080, 83, 90, 1288, Ann. 392/262).

Especially melon-ester semi sponding benz-pinacones and -pinacolines of tetra-phenylmethane dyes are better (8.60/1381, 2470). More suitable for photographic purposes are ethers, esters, amines, hydrazones, etc., of carbinols, and also of mixed triphenylmethane azo dyes which, however, are not always colorless or'yellow (3.33/2860-72, 34/880-84, 3384,

57/452, Ann. 334/146, C. C. 1924, I, 1027, J. Ch. Soc. 1917, Vol. 111/815, German Patents 57,452, 58,572/3/4, 58,893, 189,936. 282,198, 288,838, 290,- 102, British Patent 256,775, French Patent 579,- 838). Most of these derivatives are entirely stable in the'presence of sodium carbonate and often also in the presence of nxed alkalies (8.45/2910, 12, 14), but generally'they are easily split by acid, as in the case of triphenylcarbinol not substituted by amino groups (8.35/3016) with very few exceptions (3.65/919). Coupling derivatives of carbinols are prepared with salicylic acid chloride, hydroxy-benzylbromide', hydroxy-benzylamine, amino-a-naphthol, m-aminophenol, hydroxy-diphenyl-hydrazine and -oxime, etc. As most of these C-derivatives are indifferent to silver. bromide gelatine, color fog need hardly be feared. Coupling takes place in the presence of sodium carbonate or even weaker alkalies. but sometimes also in the presence of fixed alkalies or ammonia. The liberation of the basic dye by acids is best done in. the presence of phosphotungsticorsilicotung'stic acid, which forms an insoluble salt and so prevents diilusion of the dyes within the triple layer.

Carbinol ether: are usually colorless oryellow andvery easily saponinedby acids (3.33/3356,

46/2277, 42/2390). Their usually quite exceptional stability to the hydrolyzing action of alkalies and sodium carbonate solutions is remarkable.

Carbine! esters can be prepared observing special precautions, but their stability for photographic purposes is usually too slight.

C'arbinol-anilides and -aminobases are prepared by the action of aniline and other organic bases or ammonia-on dyes (3.45/2910, 65/919,

' 37/2871, 3159), but not with the same facility for all tri-phenylmethane dyes (B.46/952,963): however, in some cases dimethylaniline is an unexpected aid (13.61/1297).

Carbinol-phenyl-hydrazones and -o::imes are I stable to bicarbonate, but are saponifled even with cold dilute mineral acids (338/211, 27/1404,

snnmou To 11 Elimination of acyl groups in re-oxidation of leuco-f orms is not limited to genuine vat dyes, but may also be found in other dyes (3.33/1567,

31/3241, 71, 17/380, 39/916, /2072, 0. C. 1924, II, 2521). It may also serve for coupling oil in the presence of precipitants for the dye formed.

V. FORMATION OF CHROMOPHORES BY COUPLING AND acm-sru'rrmo chromophore which alone or together with auxocnrome groups in the original coupling component, yields genuine dyes.

Benzoquinone itself is, however, hardly suitableasadye,especiallyasi tisnotinsolublein water. Condensed quinones, such as the yellow a-naphthoquinone and the more orange naphthoquinone have a more pronounced indino vidual color; the color of 1,4 and 1,2-anthraquinone and the corresponding naphthanthraquinon'es, as well as their tetraand octo-hydro derivativea'and theusually yellow diaryl-benzoquinones, are still more intense. All these are formed by coupling of the proper phenols, etc., with the developer and splitting of the indophenol, etc., formed-during this process. By introducing halides and other substituents, preferably in the quinone nucleus itself, the coloring power is considerably increased. An example oi the formation of a quinone chromophore in this manner, the coupling development or anthranol and monobromanthrone with p-aminodimethylaniline, is mentioned, where the an may be very easily regenerated by splitting with acid (B. 40/525, 529). The same applies to arylsulphonyl-meso-anthramine (BAD/520) and for diphenyl -methanesulphone (3.33/965) methylene group of which can also be mono-brominated 40 for easier coupling.v The substitution products of these basic substances behave similarly, even if diiferences in the coupling speed are present. Coupling with anthranol, which is insoluble in sodium carbonate, or with anthrone, proceeds rather slowly in development, but ,is better after halogenation of the methylene group of 'anthrone. Leuco-sulphuric acid esters (German Patent 567,845, British Patent 340,983) can also be obtained from substituted anthranols, or from the I 50 derivatives of meso-anthramines which are more suitable on account of'their stronger acid character similar to meso-bromanthrone. Even if the stability of anthraquinone vat dyes leaves nothing to be desired, quinone dyes prepared with 5 the quicker coupling phenols, anthranols, etc.,

are to be recommended.

The new principle 01 color photography consists, then, in adding to the three layers; phenols, naphtnols, anthrols, arylsulphonylamines, aro- 6o matic amines and diamines, and the like, which i are properly substituted by auxochrome groups or attached hetero-rings, and are insoluble in alkaline developers containing sodium carbonate or which do not appreciably diifuse under these conditions and yet couple quickly during development with p -amino-dimethylaniline or other diamines to insoluble indamines yielding the corresponding quinone with dye character by splitting, the dilute acids. Combinations with acid methylene compounds are less suitable, since I ketonic acids and ketopyramlones formed in this process do not show a pronounced color. One could, of course. also couple added components of suitable character by coupling with p-aminophenol, 4-amino-resorcin, p-amino-salicylic acid,

' been made developable, or by co-oxidation with other agents, or by the action of p-nitroso-dimethylaniline, or the like. The residual component could, of course, also be converted to the colored quinone by oxidizing agents directly or after previous nitrosation which is, however, more diflicult.

If the residual coupling component is not washed out, but allowed to remain in the image,

7 then it may also contain sulphoneor carboxylic acid groups, preferably in such a position to hydroxyl that they are split with greater ease during coupling. If quinones of basic character are formed during acid splitting, the presence of phosphotungstic or other inorganic or organic precipitants is desirable in order to prevent difiusion. Quinones are usually formed during acid splitting; under certain conditions, however, or with improper choice of components and developers, the hydroquinone form can also appear (Ann. Bd. 392/17, 418/259), and even addition of the split diamine or aminophenol to the quinone can be brought about.

It would be impractical to add the finished leuco-dye derivatives to the layers, as for example, azomethine from anthranol and p-nitrosodimethylaniline or p-nitrosophenol, because it is too difiicult to wash the residual leuco-phenol compound out with caustic alkali after preliminary development and splitting to the quinone dye, unless the leuco dye derivative is very simply constructed.

VI. SYNTHESES OF COUPLING COMPO- NENTS FOR QUINONE DYES Since splitting of indophenol formed during development is done with acids, no strong inclination to form hydroxy-quinones and their polymerization products exists, as in development with simply substituted hydroquinones in the presence of sodium carbonate and alkali. According to German Patent 236,074, even yellow dianilidoand di-p-anisidino-benzoquinone can be used for dyeing from alkaline vat, without the danger of mis-colored condensation products being formed. Also substituted toluquinones and naphthoquinones behave essentially more favorably than mono-derivatives of benzoquinones (13.44/ 1648, 53/447, 450). It isnoteworthy that diaryland especially tetraaryl-benzoquinones are.

' less these components are added to the layers in the form of completely insoluble salts with phosphotungstic acid or other precipitants. It is, however, more certain if methylaniline or diarylamine are introduced as auxochrome groups; under certain conditions, acylation of the nitrogen still containing a free hydrogen atom is also recommended, since even the simple acyla nino oping properties.

group prohibits a compound from having devel- (1) Simple quinones with due character Phenylbenzoquinones are formed by coupling and acid-splitting from oand m-hydroxy-di phenyl. but they are not completely water-fast and have not sufliclent coloring power. The corresponding w-naphthoquinone (Ann. 362/318) can be prepared similarly from 2-phenyl-a-naph thol or its tetramethoxy derivative. Other arylated quinones can be obtained from components mentioned in application Serial No. 151,811, especially also with cryptophenols mentioned therein and which are substituted by diphenylmeth- 'ane or triphenylmethane groups (B. 60/2244-54, 2373-78, etc).

Higher molecular diarylbenzoquinones and -naphtho-quinones, etc., are formed by aggregation of two molecules of benzene, toluene, xylene, phenol, phenol ether, cresols, cresolethers, resorcin mono-ether, naphthols, Michler's hydrol, and the like (55/3105-16, 60/ 1440-51, 66/792, German Patents 459,739, 508,395, 565,423, 566,521, 568,968, British Patent 390,029, German Patent 71,306, 13. 32/2150, 2148, 33/2865, 41/990, Phot. Korr; 1932/4). If these quinones contain another free hydroxyl group in the side chain (B. 55/3114, 60/1442, 1444), then they can be al koxylated by alcohols or phenols or acylated by acids, preferably before condensation; high-molecular or colloidal substances, such as polymer-' ized vinylbenzylbromide (B. 50/46) or acrylic acid chloride (German Patent 547,645) and other polymerizing compounds may also serve for this purpose. The color which is usually yellow is not essentially changed by this, unless strongly coloring auxochrome groups are also introduced into the attached aryls.

Self-colored condensed quinones are prepared by coupling and acid-splitting from the corresponding phenols, naphthols, anthrols. naphthanthrols, etc. Anthraquinones hydrated in one or both nuclei can be obtained in the same manher from hydrated anthranols or anthrones, meso-brom-anthrones or anthranols (B. 58/2670, 78, 93). These tetraand octo-hydrated anthraquinones and phenanthrene quinones are usually colored rather intense yellow or orange (B. 58/2670, 77, 79, 92, 94, 62/2337-72, 63/1484, German Patent 502,043) and also red ,B-amino derivatives are obtainable (B. 58/2690, 96, 64/1152).

Multiple quinones obtained, for example, by

coupling and acid splitting from oo'- and mm'- dihydroxydiphenyl'belong to this group. Substituents can also be introduced with these for the purpose of changing the color. One could also alkoxylate or esterify one hydroxyl group in the numerous isomers of dihydroxydiphenyl by highmolecular or polymerizing residues, as for example, o-vinylbenzyl bromide and acrylic acid chloride, and then couple one half during development to indamine, the substituted high-colloidal quinone is then liberated from these by subsequent treatment with acid. Several molecules of a quinone can also be connected together by nitrogen, sulphur, oxygen, etc., ,(B. 5/600, C. C. 1932,11, 2451, B. 59/1268, Ann. .416/164, German Patent 175,070). On the other hand, highmolecular and often also high-colloidal polyquinones are formed by combination of phenol sulphonic acid chloride orsalicylic acid chloride,

. ,a-naphthol-2-carboxy1ic. or sulphonic acid chloride, and the like, withthe basic chain members mentioned in application Serial No. 151,811, or of aminophenols and aminonaphthols with acid intermediate members also mentioned there, if the indamines or indophenols formed in coupling development are decomposed by acid. More pronounced colors are, of course, also obtained in this case only after theintroduction of auxochrome groups. In order to avoid diflusion as much as possible, the high-molecular and colloidal coupling components mentioned there must be prepared and added to the layers.

In many cases,- it is not easy to prepare the phenol, naphthol, anthrol, etc.,-belonging to the quinone dye, it the auxochrome groups required are to be in the correct position. Re-conversion of quinone into substituted phenol is occasionally efiected by first forming monoxime (nitrosophenol) or phenylhydrazone (azo dye) and reducing this to the corresponding aminophenol. Diazotization and boiling with alcohol yields simply substituted phenol, or naphthol under the most favorable conditions; otherwise, only their bromoor chloro-derivatives are obtained which, as is known, also couple with displacement of the halide group. In multivalent quinones it will suffice to reconvert one quinone group in this manner.

(2) Quinoaes with monochrome groups It has been mentioned several times that greatest increase of the dye character of quinones is effected by the introduction of auxochromes, as

for example, amino-, alkyb, arylaminoor also acylamino groups, less so by aikoxylation or esterification of hydronlor mercapto groups, and least by aryls and the diand triphenyl-methane m. These auxochrome groups are most strongly active'in condensed aromatic or heterocyclic systems, as in naphthoqmnones. 1,4-anthraquinone and ordinary anthraquinone, etc.

Detailed description of the introduction of these groups into the molecule of the basic phenols or naphthols concerned would serveno purdensed in this manner with diphenyl methane or triphenyl chlormthane. Two molecules of oaminophenol or 2- or 4-amino-a-naphthol are chained by ppor mm'-dibromdiphenyl in the presence of copper powder, after which both imino-hydrogenatoms are substituted by stearylj or ceryl residues.

Substituted quinones are obtained from the quinones themselves in the simplest manner by addition or exchange reactions. It may often be advisable to reconvert quinone into the basic phenol or naphthol through the monoxime or phenylhydrazone, as previously described; that is, if they are obtainable at all with the given configuration of the quinone.

As already mentioned, the auxochrome groups may not only be introduced into the quinone nucleus itself, but also into similar and heterocyciic, rings condensed with it, or alsointo other quinone nuclei connected with the former by saturated or unsaturated intermediate members; such as, the methylene, ethane, ethylene, butadiene group, etc., and their preparation is relatively simple if glutaconic dialdehyde is used (B. 59/2658) which is extensively employed in modern synthesis of This may be used especially for consensitixers. necting two molecules of amino-s-naphthol, because the color of the dianil is not necessarily disturbing, even less so when using maleinic dialdehyde.

n it is desirable to introduce high-molecular alkyls, aryls or acyls into the hydroxy-,' ainino-,

Y sulphydril-, anilido groups, etc., this must not be done directly. Ethylene oxide or anthranilic acid chloride, or the like, can first be allowed to react and then, in turn, the high-molecular groups or connecting members, if chaining of molecules is desired. 4

Components with heterocyclic rings attached are suitable not only or production of yellow and red colors, but for blue quinones of which only few are known, not counting the condensation products oi dialdehyde thym q inone with aromatic amines-(B. /1502); at any rate, the proper derivatives of isopropylphenol are not easily obtainable.

From'the indamines formed by many mono-' valent polyvalent coupling components, such as those mentioned in application Serial No.

Production methods can be usedhere which otherwise are notused in dye technique: for example, condensation of halogenated molecuks among themselves .or with amines, mercaptans, sodium arylsulphamide salts,,etc., in the presence of silver or copper-powder, also with sodium compounds of malonic acid ester, phenyl acetic ester and other acid methylene compounds. (3. /320.

950, 59/2066. 55/3118). llagnesium organic l5 compounds-can frequently be used, as its price is not of great importam'ae. l'br o-chlorphenol or 2,5-dichlorphenol can be converted with salts of high-molecular fatty acids, with w boxylic acid amines or sodium salts of sulphonic acid amides. In more complicated and unsaturatedoompounds, especiallythoeeoithe aliphatic serieaheatlngcannotbeearriedtoofaahowevensinoe'explosionofthe'chaineasilyoecurs 151,811, quinones and diquinones with heterocyclic rings attached are formed by splitting with acid. These are sumciently insoluble, if combined with the loading and connecting members mentioned therein. Bensocarbaaolquinone, for example,is obtained from the diasotiaation product of l-amino carbaaol and boiling to l-hydroxy-carbasol, similar to S-hydroxy-carbaaol (8. 46/3717, 34/1583, 55/235245) by coupling and splitting with acid. Blah-molecular naphthoquinone-2,3-carbasol gives a pure yellow color, which can also beprepared from the corresponding hydroxy-derivative by oxidation or coupling and splitting with acid (German Patent 454,403) Coupling products which yield usually yellow to orange colored aslneor acridine quinones are obtained from hydroxylat'ed phenaainesand acridin'es during condensation with 2-chloror i-chloror i-brom-s-na mthol or a mixture of the chloro-derivatives (56/2390, German Patents 355,902, 368,188/9, 855,491, 357,286).'

(a) Higher molecular I Bomematerial for the synthesis ofviolet to (a some) Z-chlor-s-naphthoI can also be ooublue-violet and perhaps alaogreenish-bluenaphr purpose of explaining the nature of vat dyes (13. 44/1650, 53/446). 'It is evident from these studies that a-naphthoquinone yields red dyes by addition of benzidine, .toluidine, diamino-diphenylurea, -diamino-diphenylmethane, etc.,' if necessary with two molecules connected. The tone of these red dyes can be changed to blueviolet by acylation to a most pronounced degree in the case of the bis-derivatives obtained with Y the aid of dio-anisidine and o-ethoxybenzidine (B. 53/452. 449, J. f. pr. Ch. Bd. 92/370).

The starting products for formation of these dyes by coupling development and acid splitting are relatively easily prepared from 2-chlor-anaphthol which can now be produced with great.

color is not only deepened, but components are obtained which hardly diffuse in alkaline solutions.

Instead of o-dianisidine and o-ethoxybenzidine, their higher analogues, ethers obtained with stearylor ceryl bromide, can also be used as binding members. One can also start from 2-amino-a-naphthol and convert this or its monoacylor sulphonyl derivative or the product obtained by the action of ethylene oxide, with dibromdiphenyl.

chlorinated porm-aminodiphenyl can be al- Furthermore, a brominated or lowed to react on the same, and two molecules chained with their external amino groups through phosgene or dibasic acid.

Dye derivatives of p-naphthoquinone can be obtained in a similar manner by allowing 3- chlor-p-naphthol to react with the high-molecular auxochromes mentioned, or by forming these auxochromes through connection of several mole. cules of 3-amino-B-n-aphthol or 3-amino-u-naphthols with the polybasic acid chlorides mentioned, also by means of intermediate members acting as enlargers. In both cases it is, however, advisable to have a non-discardable substituent in the 4-position, as for example, alkyl, carboxylic acid amide or ketone group, etc., so that the amine liberated by acid splitting is not added in the 4-position'wlth formation of hydroxy-naphthoquinone im'ides (Ann. 392/17,

41-6, 259, 358/825, Cpr. 192/1664, German Patents 414,427, 415,317-320, 444,518, 445,525). For the same reason, it is recommended to occupy this position of a-naphthol derivatives by a non discardable radical leaving the 2-posltion free, although here the probability of an addition is much more remote.

exchanged for aniline, phenyldrazine, semi-car- If, however ,.the halide of the 4-chlor-derivatives of uand ,3naphthol is anilldo-a-naphthol is, unfortunately, not easy.

The following methods are open: The two bromine atoms of 2,3-dihydro-naphthalenedibromide are exchanged for two molecules of aniline or methaniline and. the product obtained is oxidized to the 2,3-naphthalene derivative; a hy-- droxyl group is then introduced into the 1-position by any suitable method. Of course, 2,8- dlchlorn-aphthalene could also be converted similarly with two molecules of aniline or methylaniline in the presence of copper powder (BAG/1783, 46/528, 1052, 54/25, 50, Ann. 444/146, 155). A chlorine atom is introduced into the 2-position of 3-methylanilino-a-naphthol, and this converted'with one molecule of methylaniline, or the 2,4-diha1ide derivative, is prepared in which only the 2-halide atom reacts with an aromatic amine, whereas, the 4-chlor atom is liberated during indamine coupling, or it may be removed by catalytical reduction with nickel at ordinary temperature. An acetyl group can also be introduced into the 2-position and this replaced by the amino group on the oxime (3.48/1704,

, 54/1299), or the 4-halide derivative is prepared (B.28/3053, 44/1337, 866, 56/972, 2043) and this coupled to the Z-azo dye which also yields the 2-amino-derivative by reductions; or 2-carboxylic acid is prepared and this converted to the amine through the 2-azide which could eventually be arylated (358/2850). 2-amino-3-aniline-a-naphthoquinone is also colored blue, but

a-naphthol analogously substituted is not very bazide, etc.,.or their acyl derivatives, fl-hydroxy- I naphthoquinoneim'lde derivatives or quinone-azo dyes are obtained by coupling and acid splitting (328/546).

quinone indigo blue and the analogous di-.

anisidino derivative are colored green-blue (3.58/1'130, 1137) but the production of 2,3-distable, unless it is added to the layer as completely insoluble phosphotungstate.

(5) Blue naphthoquinohe dyes with hetcrocycle These dyes are obtained by linking on a thiodiphenylamine or oxazine ring (346/269, 57/496, Ann, 247/281, 292, 297). In 2-chlor-3-anilinoa-naph-thol the chlorine is converted with sodium disulphide and then reduced to 3-mercaptan which is-oxidized to thiazine by atmospheric oxygen. The quinone concerned is colored blue its N-methyl derivative, however, and the product obtained with fl-naphthylamine is greenish-blue.

Instead of aniline, its o-disulphide can also beof 2-chlor--naphthol can also be condensed with the disulphide of o-amino-thiophenol, then reduced andthe ring closed by heating. Instead of aniline, also its o-disulphide can be allowed to act on 1,3-dioxynaphtha-1ene, or o-chloraniline wit'hchlorination in the 2-position and closure of the hetero-ring. The most suitable for conversion with these o-benZene derivatives is 2,3-a-naphthol which is diflicult to prepare; however, 2,3-dibrom1,4-naphthalene diamine can also be used and one amino group replaced by halide or hydrogen after connecting the heterocyclic ring to the diazo compound; the other one is replaced by a hydroxyl. Similar quinone dyes can also be obtained from 5-brom-3-chlor-pnaphthoquinone or from correspondingly substituted naphthols (3.57/499) This may be done still more easily by reduction or 6-nitro-derivatives of thiazines and oxazines alkylated in the amino group. and arylsulphonylation or replacement by hydroxyl (3.56/2389, 8'1) also by reduction and alkylation or acylation of the corresponding thiazones and oxarones (ass/2390,

An acetylamino group in the thiodiphenylamine ring shifts the color to green. Also alkylated mercaptans prepared from the 2-chlor-derivative are strongly colored. The simple ones are violet and those which are substituted by an acetyl amino group are indigo blue (Ann. 247/287, 296, BAG/3040, 46/1780, 47/925, 1100, 54/1578,

56/2563, J. 1. pr. Ch. 107/358, 383, loan, 19,

(6) Blue naphthoquinone dyes with malonic acid groups The corresponding substitution products of a-naphthol are, of course, only obtained by forcei'ul condensation of 2-chlor-a-naphthol with sodium malonic ester in the presence oi silver or copper,- or of 2,3-dichlor-a-naphthol which is dimcult to prepare, so that reconversion of the quinone dye at least with mono-derivatives, ap-

pears to be more advisable (3.33/566-78, 2402-24,

It will be apparent from the foregoing description that the dye compounds incorporated in the photographic layers may be dyes themselves or leuco derivatives of dyes, and where reference is made in the claims to coupling derivative-oi a dye compound" it is understood that this reference is to either the dye or the leuco derivative of the dye. These dye compounds are incorporated in the gelatin layer as a non-wandering coupling derivative capable of being split or converted to form the image dye. This splitting or conversion may be brought about by (1) hydrolysis, (2) oxidation, (3) reduction, ,or (4) a combination oi two of these methods, as described in the present specification.

By "couplingderivative or a dye compound or "coupling derivative oi a dye" I mean dyes or dye pling derivatives of dyes or dyeintermediates used in my process must be those which are soluble in strongly alkaline solutions. a

I claim:

1. The method of forming a colored photoraphic image in a silver halide layer containing a coupling derivative, soluble in strong alkali, o!

a dye compound, which comprises exposing the of the dye irom the unexposed portions of the layer and developing it in a coupling developer to form a dyeimage soluble in strong alkali. removing the coupling derivative 01 the dye compound i'rom the unexposed portions of the layer in a strong alkaline solution, and regenerating the original dye in the exposed ayer;

2. The method of forming a colored photographic image in a silver halide layer containing 1 a coupling derivative, soluble invstrong alkali, of

portions or the a dye compound, which comprises exposing the layer and developing it in a primary aromatic amino developing agent to form a dye image insoluble in strong alkali, removing the coupling derivative of the dye compound from the unexposed portions of the layer in an alkaline solution, and regenerating the original dye in the exposed portions of the layer.

3. The method of forming a colored photographic image in a silver halide layer containing a coupling derivative, soluble in strong alkali, or a dye, which comprises exposing the layer and developing it in a paraphenylene diamine developing agent to form a dye image insoluble in stroll! alkali, removing the coupling derivative 01 the dye from the unexposed portions of the layer in a sodium hydroxide solution, .and regenerating the original dye in the exposed portions of the layer.

4. The method of forming a colored photographic image in a silver halide layer containing a coupling derivative, soluble in strong alkali, of a dye, which comprises exposing the layer and developing it in a paraphenylene diamine developing agent to form a dye image insoluble in strong alk'ali, increasing the solubility of the residual coupling derivative by coupling it with a solubilizing compound and removing the last mentioned coupled dye derivative from the unexposed portions of the layer in a strong alkaline solution, and regenerating the original dye in the exposed portions of the layer.

5. The method of forming a colored photographic image in a silver halide layer containing a coupling derivative, soluble in strong alkali, of a dye, which comprises exposing the layer and developing it in a paraphenylene diamine developing agent to form a dye image insoluble in strong alkali, increasing the solubility of the residual coupling derivative by fogging the layer and coupling the residual coupling derivative with a solubilizing developer, removing said last mentioned coupled derivative from the unexposed portions of the layer in an alkaline solution, and regenerating the original dye in the expom portions of the layer.

.6. The method of forming a colored photographic image in a silver halide layer containing a coupling derivative, soluble in strong alkali, of a dye, which comprises exposing the layer and developing it in a paraphenylene diamine developlns agent to form a dye image insoluble in strong alkali, removing the coupling derivative of the dye from .the unexposed portions of the layer in a strong alkaline solution, and converting the coupled dye derivative in the exposed portions of the layer. to the original dye by chemical action.

'l. The method of forming a colored photographic image in a silver halide layer containing a coupling derivative, soluble in strong alkali, oi

a dye, which comprises exposing the layer and developing it in a paraphenylene diamine developing agent to form a dye image insoluble in strum alkali, removing the coupling derivative reduction.

strong alkali, removing the coupling derivative of the dye from the unexposed portions of the layer in a 'strong alkaline solution, and convert ing the coupled dye derivative in the exposed portions of the layer to the original dye by 9. The method of forrninga colored photographic image in a silver halide layer which comprises condensing a vat dye 'with a phenolic component to form a coupling derivative soluble in strong alkali of the vat dye, incorporating said coupling derivative in the silver halide layer, exposing the'layer and treating it in a silver halide developer whose oxidation product couples with the coupling derivative to form a dye image insoluble in strong alkali, treating the layer in a strongly alkaline solution to remove the undeveloped coupling derivative, and treating the layer in a solution which splits' off the developed phenolic component and regenerates the original KARL SCHINZEL.

CERTIFICA'I'S OF CORRECTION.

Petent H9.- 2319,5141. July 15, 19M.

KARL scnmzu.

It is herpby cerfiifiedthat error appears in the printed specification of the abeve nunbenee. pat'ent rewiring correction as follows: Page 11 riret eolumn, line 71;, for'sylit" rea1 1-apli Ltpage 16, first oolu m, line' 67,

018 11;: 1, forth'e word "soluble" read --inec luble-; and that tlie said Lettors Patent should be read vkith this ,correction therein that the same may cqnform, to the record of the case in the Patent office.

' Signed Ana sealed uns- 9th da of Decanber, A. D. 19m.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents. 

